I don't get it! I have been using Harbor Freight Carpet Cutter blades in 3 different brand 45mm rotary cutters, ever since I first read about them here. I have used one blades for months at a time. About the only time I come up with a dull blade is when I am careless and leave a pin on my cutting mat. Otherwise, I cut lots of scraps and yardage and have no problems. I have never, ever found one to be dull.
My cutting mat is over a year old but it is a good cutting surface. There is absolutely no drag or anything that would cause the blade to not cut. I double fold my yardage, so I am cutting through 4 thickness. I don't trust myself to hold the ruler on 8 thickness of fabric. I do know that with an old mat that is full of fibers from much cutting, there is a drag on the blade.
Why not invest $2 in one package of blades (and be aware there are 2 in a package - some people have put both blades in their cutter) and give them a try? You decide for yourself. And if your mat is old as the hills and has seen its better days, consider buying a new mat. These blades are designed to cut through the jute backing on carpet, so surely they can handle a few pieces of fabric.
By the way, why have we not heard from one person who returned their blades to the company and then reported the response from the company? I am waiting to read about those comments. If we have complaints, why not take the to the company? Why do you allow yourself to be ripped off - even for $2. blades.